Prior to surgery, it is often necessary to register an anatomical structure within a medical workspace, i.e., to determine a spatial location of the structure or of a partial region of the structure, such as a three-dimensional position of characteristic points or landmarks on the structure. These characteristic points or landmarks can be used in a hip operation, for example, to determine the spatial location of characteristic planes. From the location of the characteristic planes, the inserted position of a hip joint cavity can be determined.
If, in a hip operation, recordings are taken of the pelvis using a C-arm, then it is difficult or impossible to identify a characteristic or unique contour of the pelvis due to the different types of tissues and operating instruments that may be present. It also can be difficult to detect a contour or characteristic point since the anatomical structures are different for different patients, such that when registering the anatomical structure inaccuracies may be introduced. This can cause problems during or after surgery.
A method and device for registering a pelvis are known from WO 2005/084541, wherein a pointer comprising trackable markers that are detectable by a tracking system is used for acquiring points.